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Ups and downs in understanding stellar variability

Ups and downs in understanding stellar variability. Wrocław 20.08.2013. Mid 1960ties. Variability of Cepheids and RR L y r ae stars explained. Radial pulsation hypothesis (Ritter 1879 ) confirmed ( Shapley 1914, Baade 1926 )

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Ups and downs in understanding stellar variability

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  1. Ups and downs in understanding stellar variability Wrocław 20.08.2013

  2. Mid 1960ties. Variability of Cepheids and RR Lyrae stars explained Radialpulsationhypothesis (Ritter 1879) confirmed (Shapley 1914, Baade 1926) Differencebetween RR Lyraestars and Cepheids (Baade 1946) Stars as heatengines (Eddington 1917) The -mechanism critical role of theHeIIionizationzone (Zhevakin, 1953) OverstabilityinrealisticCepheidmodels(Baker & Kippehahn, 1962, 1965) Nonlinearmodeling of RR Lyraestars and Cepheids (Christy , 1965, 1966)

  3. Major openproblems of late 1960ies 1. Convection /pulsation interaction. The red edge of the Cepheid Instability Strip (Baker & Gough, 1979) 2. Drivingmechanism for nonradialoscillationsinβCepheistarsproposed by Ledoux (1951) Nonadiabaticcode for nonradialoscillationsintegratedwiththestellar evolutioncode of Kippenhahn & Weigert . Mixedmodesinevolved MS stars, unstableintheδScutiTeffrange but no instabilityintheβ Cep range (Baker & Dziembowski, unpublished)

  4. Why Cepheids and RR Lyraestarschoose onlyradial modes ? Verystrongdamping of quadrupolarmodesinradiative interior (WD 1971) Unstabletrappedmodes of moderatedegreesinthevicinity of radial F and 1O modes In Cepheid (Osaki 1977) and RR Lyrae (WD 1977) models Instability extends to high degree f-modes but the driving effect changes and to hotterstars (Shibahashi &Osaki 1981). Are high degreemodesexcitedinstars ?(Balona & WD 1999)

  5. Multiperiodic variability in the Cepheid Instability Strip Common amongScuti stars, rare in RR Lyrae and Cepheids. Same drivingeffect but resonantvsnonresonantamplitudelimitationmechanism Beyond the linear theory : amplitude equation formalism, parametricresonance(1982) Application to  Scutistars 1985-1990, collaborators: M. Królikowska, A. Kosovichev) P. Moskalik (MSc 1984) M. Królikowska (PhD 1988), R . Nowakowski (PhD 2003)

  6. Asteroseismologyinthepre-CoRoT era  Scutistars - embarras de richesse (1995 -collaborationwiththe DSN M. Breger, G. Handler,……. A.Pamyatnykh ) Prospects for sounding internal rotation (1996, collaborators: M.-J. Goupil, E. Michel, P. Goode) Lostoptimism - troublesomehigh-degreemodes (1997, 2010 collaborators: L. Balona, M.-J. Goupil,J. Daszyńska-Daszkiewicz, A Pamyatnykh) Back to ground-base data. Observationalmodeidentification (2003-2005 collaborators: J. Daszyńska-Daszkiewicz, A Pamyatnykh, M. Breger, G. Houdek, W. Zima)

  7. Double modeCepheids Petersen diagram and the huge mass discrepancy (Petersen 1973) Appeal to atomic physicists for a reexamining heavy element opacities(Simon 1982) OPAL(Iglesias et al. 1992)and OP(Seaton 1992)projects The huge mass discrepancy removed (Moskalik et al. 1992)

  8. WhysomeCepheids and RR Lyraestarschoose double modepulsation First double mode RR Lyrae star(Jerzykiewicz & Wentzel 1977) Only-F, Only 1O, and EO regions(Baker & von Sengbusch 1970, Stellingwerf 1975) The 1:2 resonance between F and 2O mode in the EO region (1984, collaborator G. Kovacs) The same resonance may alsoexplain also theBlazkho effect in RR Lyrae stars(Moskalik 1985, PhD) Amplitude formalism for radialmodesdeveloped to cubic terms (Buchler& Kovacs 1986) support for the role of the 1:2 in double mode pulsation but Not always elegant means correct - no resonanceat realistic stellar parameter. TheFlorida-Budapest(Kollath et al. 2002) and Warsaw (Smolec & Moskalik 2008, 2010) convectivecodes Mayberesonancesafterall

  9. Double- and triple-mode Cepheid from OGLE survey SMC LMC Petersen diagrams for Magellanic Cloud Cepheids (Soszyński et al. 2008, 2010) Deduction of stellar parameters, search for resonances(2005-2013, collaborators: Moskalik, Smolec) Only PS/PL 0.6 could not be explained in terms of radial modes.Perhaps 1O+fl(l=42-50)

  10. The 1:1 resonances and the Blazkho effect The amplitude equations up to cubic order for nonradialmodes (Buchler & Goupil 1984,1997,Van Hoolst 1994) radial/dipolar mode coupling as the cause of Blazkho effect (1998-2004 collaborators: T. Van Hoolst, S. Kawaler, S. Cassisi, R. Nowakowski, T. Mizerski) dipolarm=0orm= 1pair Elegant but ratherunlikelysolution of the problem

  11. The opacity mechanism in the Fe-bump zone and B-type stars (Simon 1982, Iglesias et al. 1992, Cox et al. 1992) Not onlyβCepheistars (1992 -, collaborators: P. Moskalik, A. Pamyatnykh, H. Cugier, M. Jerzykiewicz, L. Balona, G. Handler, J. Daszyńska-Daszkiewicz, W. Szewczyk) Parallelworks: (Gautschy & Saio, 1993, Lee 1998, Townsend 2005, Saio et al. 2007, Miglio et al 2007) sdBstars(Charpinet et al. 1996,... ) New data , newproblems

  12. Red giant pulsationoverstabilityvsstochasticdriving Solaroscillations - stochasticdriving (Leighton et al. 1960, Ulrich 1970, Ando & Osaki, 1975, Goldreich & Keeley 1977) Mira (Fabricius 1596), - overstability , ( Ostlie & Cox 1986, Xiong et al. 1998) Microlensingsurveysinspiread by Bohdan Paczyński Many PL relations from MACHO and OGLE (the OSARGs) The best of CoRoT and KEPLER  UMa, OSARGs(2001 - collaborators D. Gough, G. Houdek, R. Sienkiewicz, I. Soszyński +, B. Mosser +) Parallelworks: J. Christensen -Dalsgaard et al. 2001, Kiss & Bedding 2003, Xiong & Deng2007, Dupret et al. 2009)

  13. Thedecade of spacemissions and massivephotometry old and newproblems

  14. Norman Baker died on October 11, 2005 Bohdan Paczyński died on April 19, 2007 Robert Christydied on October3, 2012 Robert Buchlerdied on October 16, 2012 Arthur Cox died on March 12, 2013

  15. Thankyou for coming to Wrocław

  16. The opacity mechanisminradiative and convectivelayers a  Sct star model

  17. a  Dor star model

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